Nuclear plants have various safety systems to ensure that the nuclear fuel in the reactor core remains cooled in all credible accident scenarios. One such scenario is a “loss of coolant accident,” in which an external pipe is postulated to break, allowing a large amount of water to escape from the reactor cooling system. This water may dislodge solid debris from neighbouring pipes or other reactor structures. The water, along with some of the dislodged debris, will flow to the lowest parts of the reactor building into a sump. Plants are equipped with safety systems that pump water from the sump back into various reactor cooling systems. Strainers on the pump intakes ensure that any debris large enough to clog equipment in these systems is prevented from entering. Depending on the type of debris, the first layer to deposit on the strainer may form a finer filter than the underlying screen, and catch many smaller particles.
Strainers must have enough screen area that the debris layer on the strainer is not too thick to cause unacceptably high restriction to flow. Strainers must also be as small as possible to fit into the available space. Therefore compactness, i.e., accommodating the most screen area in the smallest volume, is important.
Conventional strainers in many nuclear plants are simple box-type devices mounted over the pump intakes. Newer more advanced strainers often have an irregular surface to increase the surface area.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.